Embodiments of the present disclosure relate to sensor arrays, and more particularly to construction of modular sensor arrays.
Sensors or transducers are devices that transform input signals of one form into output signals of a different form. Commonly used transducers include light sensors, heat sensors, and acoustic sensors. A wide variety of various applications, such as biomedical non-invasive diagnostics and non-destructive testing (NDT) of materials entail the use of sensor arrays, where the sensors are often configured in two-dimensions (that is, the X-Y plane). Moreover, applications such as medical and industrial imaging, non-destructive testing (NDT) and inspection, security, baggage scanning, astrophysics and medicine may entail the use of sensors that encompass large areas. In the field of medical diagnostics, such as, but not limited to, X-ray, computed tomography (CT), ultrasound and mammography, it may be desirable to employ sensors that encompass large areas. For instance, in an X-ray imaging system, large area transducers may be useful to encompass the area of the X-ray detector. Moreover, in non-medical applications even larger arrays may be desired.
As noted hereinabove, large area detector arrays have desirable characteristics for certain applications. Sensor modules may be arranged to form the large area detector array. Furthermore, it is desirable that the edges of the sensor modules in the array are aligned with the edges of neighboring modules without any significant gaps or offsets. However, it is becoming increasingly difficult to achieve this tileable structure. Particularly, since the sensor detection element must be electrically connected to readout application specific integrated circuits (ASICs), the high density of interconnect requires a close correspondence between the ASIC contact pads and the sensor contact pads. Typically, the ASIC has contacts disposed on only one side. Furthermore, the ASIC in addition to using these contact pads to couple the ASIC to the sensor, also needs to use these contact pads to make power and digital communication connections to other system electronics. Therefore, it is desirable to implement some means of connecting both the sensor and system interconnects to this ASIC surface, while also supporting the four-sided tiling structure and a high pixel pitch in the sensor.
A currently available technique typically uses a staircase array of modules where a top surface of the ASIC is directly bonded to a bottom surface of the sensor element. This requires a match between the bump bond array on the ASIC and the bump bond array on the sensor. In addition the ASIC chip extends laterally beyond the sensor element and this extension is used to place wire bonds to couple the top surface of the ASIC to a backplane layer. Unfortunately, this extension of the ASIC creates a need to raise subsequent modules vertically to create a clearance space for the wire bonds. Additionally, all the modules in this detector array are not aligned in the same plane. These offsets disadvantageously create a non-ideal imaging geometry as the different modules are at different distances from an X-ray source. In particular, when the X-ray incident direction is not normal, there can be shadowing effects when one module occludes other modules.
Presently, certain other techniques entail forming the detector array by shingling sensor modules like roofing tiles or fish scales. In this embodiment, the extension of the sensor module and wire bonds is accommodated by the space created by the angle of the sensor modules. However, the module plane normal is not locally aligned to the detector plane normal since the edges of the sensor modules do not line up. This technique presents a non-ideal imaging geometry.
It would therefore be desirable to have a sensor module that allows assembly of large area detector arrays. Specifically, there exists a need for a detector array created by arranging a plurality of sensor modules as detailed herein. Furthermore, it is desirable to tile the sensor modules efficiently to form a high-density large area detector array in order to minimize system size, complexity, interconnect lengths and enhance the performance of the detector arrays.